1. Field of the Invention
The present invention relates to corrugated tubing. More particularly, the present invention relates to multi-layer tubing having at least one region of corrugation. Even more particularly, the present invention relates to multi-layered corrugated tubing having enhanced wall thicknesses which can accommodate direct interface with various connectors. Finally, the present invention relates to thick-walled corrugated or convoluted tubing in connection with connectors literally projecting therefrom.
2. Brief Discussion of Relevant Art
Quick connect couplings have been widely used in the U.S. Automobile industry for many years. Although applicable in numerous applications, quick connectors are typically employed in fuel system and vapor recovery systems. The simplest and most cost effective design is the plastic housing female type quick connector releasably mated to a metal male tube end form. The opposite end of the female housing most typically defines a stem having a member of axially spaced barbs formed on the outer circumferential surface thereof and a nylon or plastic tubing end form pressed there over. Such an arrangement is described in U.S. Pat. No. 5,542,712, issued Aug. 6, 1996, entitled xe2x80x9cQuick Connector Housing With Elongated Barb Design.xe2x80x9d
In fluid handling systems, it is imperative that the connectors used have their male and female portions properly coupled together. Faulty connection enables an associated system to leak fluid. This can be particularly disadvantageous when the system is under pressure and the leaking connector/tubing interface expels the pressurized fluid.
Furthermore, recent federal legislation has mandated significantly reduced hydrocarbon emissions from automotive fuel and vapor recovery systems. Conventional quick connectors, although effective to mechanically maintain tubing end forms in assembly with their associated connector bodies, have not adequately addressed the federal requirements. Also, the materials employed, typically nylon 12, do not provide sufficient resistance to the permeation of hydrocarbons there though.
The permeation problem has been addressed, in part, through the development of co-extruded multi-layered plastic tube constructions containing two or more discreet layers of different types or formulations of plastic, one of which is specifically designed to provide an effective permeation resistance layer, blocking the escape of hydrocarbons from the system. In general, the most successful multi-layered tubing employs an outer layer composed of a material resistant to the exterior environment. The innermost layer is thinner and is composed of a material which is chosen for its ability to block defusion of materials, such as hydrocarbons, alcohols and other materials present in fuel blends, to the outer layer. The innermost layer may have a degree of electrical conductivity sufficient to dissipate static charges generated by the flow of fluid therein. To date, it has been extremely difficult to obtain satisfactory lamination characteristics between dissimilar polymer layers. Thus, the use of one or more intermediate layers for bonding the inner and outer layers has been proposed.
In various vehicular applications, durability concerns necessitate the use of fiberglass or stainless steel braiding as reinforcement while such configurations provide strong and durable hose configurations, braid reinforced polymeric hose configurations are difficult to adequately seal to the associated connector. Braid reinforced hoses have the additional drawback of kinking when bent or twisted to accomplish installation in the associated vehicle.
A related problem stems from dual aspects of commercially available quick connect devices, to wit: high volume and low sale price frequently necessitating the use of inexpensive, somewhat pliable materials, and complex contours of extremely small inter-fitting components. These aspects collectively increase the likelihood of misassembly. High volume production techniques, including automated assembly tends to aggravate the problem wherein misassembly or impermissible dimensional variations of the components are difficult to detect. Excessive dimensional tolerance stack-up can result in low pull-apart characteristics between the barbed stem of an associated connector and the plastic tube a producing leakage. Misassembly, such as failure to include an O-ring can also result in leakage. In the case of multi-layered tubes, dimensional and/or adhesive problems can result in mechanical delamination upon insertion of the tube over the barbed stem. Finally, mono-wall plastic tube or multi-layered structures with low hoop strength can relax over time or at elevated temperatures, resulting in leaking or weeping of fluid.
In related application Ser. No. 08/874,755, the specification of which is incorporated by reference in its entirety herein, a simple, inexpensive mechanically and environmentally robust connection between a tube end form and a connector body was proposed which eliminated the use of O-rings, wedding bands and the like by achieving a spin-welding connection. Braid reinforced tubing constructions are difficult to connect by spin-welding processes due at least, in part, to irregularities at the tube end form caused by the braid reinforcement.
Thus, it is highly desirable to provide a flexible tube or hose configuration, which is resistant to kinking and provides the reinforcement and strength of braid reinforced tubing. It is also desirable to provide a flexible hose configuration which possesses greater hoop strength then braid reinforced hose material or various thin-wall tubing configurations.
It is an object of the present invention to provide thick-walled convoluted tubing which can be successfully employed in fuel systems to provide a simple and inexpensive, yet mechanically and environmentally robust connection between the tube and a suitable connector body. It is also an object to provide a strong and inexpensive tube which is either convoluted or straight-walled and exhibits good hoop strength at the end form.
The present invention is an improved tube configuration for use in essentially fluid-tight connection with a suitable connector body which includes a multi-layer or single layer tubing having an elongated cylindrical wall having an outer surface and inner surface parallel to the outer surface. The inner surface defines an essentially unobstructed circular interior opening extending longitudinally through the tube. The tubing includes a first region in which the cylindrical wall is essentially parallel to the longitudinal axis running coaxially through the cylindrical interior. The tubing includes another region continuous to the first region, wherein the other region includes at least one corrugation in the cylindrical wall. The corrugated region has a cross sectional diameter which varies depending on position with respect to the corrugations longitudinal length and has a diameter different from the essentially uniform cross section diameter of the first region.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the invention is read in conjunction with the accompanying drawings.